Earth Sciences Report 1977-05

Earth Sciences Report 1977-05

Hydrogeology of the Brazeau-Canoe River area, Alberta

The hydrogeology of surficial aquifers and shallow bedrock aquifers of the uppermost 500 ft (150 m) of strata in the Brazeau-Canoe River map area is described. Lithology, geologic structure, topographic position and climate are the major elements of the hydrogeological regime.

Within the Rocky Mountain Main Ranges and Front Ranges limestone and dolomite are the dominant rock types. A synthesis of the geologic and geomorphologic characteristics of these rocks indicates that conduits and fractures are the major mode of storage and transmission of groundwater. Conduit and fracture permeability is likely to be better developed and more widespread in the Main Ranges than in the Front Ranges. The shaly, thin-bedded Banff and Exshaw Formations, the Fairholme Group, and the Lyell, Pika, and Mt. White Formations are the most prospective carbonate aquifers of the map area when present in topographically low positions.

Thrust faults have a strong influence on valley position and extend for many miles along strike. They have the potential of directing groundwater flow from distant sources toward localized surface discharge points within the valley floors. The valley floors serve as regional and local groundwater drains.

The most prospective bedrock aquifers of the Foothills belt occur in the Upper Cretaceous Blairmore Group. Fracture permeability is well developed in thick sandstone units and coal beds. Yields between 25 and 100 igpm (1.9 to 7.6 l/sec) may be obtained from these aquifers in topographically low positions. The black carbonaceous shales of the Upper Cretaceous Alberta Group are the least prospective aquifers of the map area.

The Upper Cretaceous to Tertiary Brazeau Formation extends to depths of greater than 1000 ft (300 m) in the Western Alberta High Plains. Intergranular and fracture porosity have a patchy distribution within these clayey and sometimes bentonitic sandstones and mudstones. Well yields are correspondingly variable, but generally fall into the range 5 to 25 igpm (0.4 to 1.9 l/sec).

The valley floor glaciofluvial and alluvial sand and gravel deposits are the most prospective aquifers of the map area. Groundwater availability and yield potential are dependent on the topographic position, permeability, saturated thickness and recharge characteristics of these deposits.

With the exception of the local occurrence of calcium-magnesium sulfate type groundwater in the Front Ranges (which can contain over 2000 ppm total dissolved solids), groundwater quality is excellent throughout the map area, and total dissolved solids contents rarely exceed 500 ppm.